The Origins of the Human Species

The story of human evolution is a long and complicated one. The line towards modern humans did not simply develop in one direction, but has had many divergences. A recent discovery in the Philippines has managed to shed light on one such divergence, Homo luzonensis.

The oldest specimens of hominin fossils have been found in Africa, dating back to six million years ago. Such fossilized skeletons suggest that these hominins were short, bipedal, and had significantly smaller brains than humans today.

“The more fossils that people pull out of the ground, the more we realize that the variation that was present in the past far exceeds what we see in us today,” said paleoanthropologist at Lakehead University in Canada, Matthew Tocheri, not related to the new discovery.

The evolution of such species into humans all started 2.5 million years ago in Africa. One group began the genus, Homo, that we belong to. They evolved traits that we are familiar with, like flatter faces, taller bodies topped off with bigger brains than others in the area. After years of development, the new species Homo erectus left the continent of Africa and moved East through Asia. However, the species we evolved from stayed in Africa. They stayed there until 100,000 years ago, where they developed into Homo sapiens. This group then began migrating around the world.

One such traveling group seems to have ended up on the island of Luzon, as shown by a recent discovery. This discovery was prompted in the early 2000's, when graduate student, Armand Salvador Mijares, from the University of the Philippines, was involved in a dig at Callou Cave on Luzon. He was inspired to intensify his search by researchers who had discovered a new species similar to humans, Homo floresiensis, on the nearby island of Flores. Mijares followed up with his own consequent discovery, Homo luzonensis.

Homo floresiensis showed considerable relation to humans and shared common traits, such as using and creating stone tools. However, these hominins differed from us with their small brains and their height of about three feet. Due to these differences, researchers have wondered about their ancestral lineage, one possible ancestor being Homo erectus. After learning about Homo floresiensis, Mijares wanted to know if its ancestors may have also migrated to the island he worked on, Luzon.

“That inspired me to go back and go deep,” said Dr Mijares as he recounted why he decided to begin digging again in 2007.

Mijares assembled a team to aid him with his work, and together they began their dig. The team eventually found an initially disappointing bunch of fossils. However, archeologist Philip Piper realized that some of the fossils resembled human anatomy; specifically a human foot. After such promising news, Mijares directed a continuation of the excavations. In 2011, the island revealed hands and femur bones, along with some teeth, all of which were surprisingly humanlike. A few years later, in 2015, they managed to dig up some more teeth, which ended up dating back 50,000 years.

The teeth in the discovery had a unique and recognizable shape, slightly different than that of human teeth. They were remarkably smaller than our teeth, and instead of just one root, they had three. These specific oral features prompted researchers to wonder about their relationship to species on the other island.

“Could it be that these teeth belonged to adults that were even smaller than Homo floresiensis?” said Debbie Argue, a paleoanthropologist not connected to the discovery from Australian National University.

The variety within the combination of the traits led the team to think that these fossils belonged to a completely separate hominin species. Many of the traits were similar to both Homo floresiensis and Homo sapiens. However, they have some differences as well that relate them directly back to early ancestors from Africa. This led researchers to ponder when exactly this species arrived on the island. Some wondered whether Homo floresiensis and luzonensis both descended from Homo erectus and moved together to their respective islands. Others thought perhaps the ancestors of Homo luzonensis travelled from Africa long before other hominins did.

A second group of researchers, in 2018, also decided to dig on Luzon, and they ended up finding stone tools next to the bones of a rhinoceros, both dating back to 700,000 years ago. Such evidence suggests that some species of hominin was present on the island already at that time.

Researchers both involved in and learning about the discovery have many varying opinions about the origins of the hominins on Luzon. Nevertheless, no conclusions can be drawn until more fossils are uncovered. Until then, whether or not the species are closely related, or were separated long before arriving to the island, remains a question with many possible answers.

[Source: New York Times]